It is known that sulfurized olefinic materials are useful as additives to lubricants, such as oil-based materials like crankcase oil, gear lubricants, extreme pressure lubricants, automotive transmission fluids, and the like. Sulfurized olefins may also be added to cutting oil and machine oil formulations to lubricate shaping operations of tough ferrous alloys, mild steel, cast iron, and the like.
In general, the olefin is heated in the presence of a sulfur-bearing compound such as under reflux conditions to a sulfurization reaction temperature. After an initial period when all or most of the olefinic material has reacted, further heating may be desirable to complete the reaction. As a rule, at reaction temperatures below about 340.degree. F., the process either takes too long or provides less than desirable products. Sulfurization catalysts have been suggested to speed the reaction. However, many catalysts provide excessive exotherm and often result in products having poor solubility in oil-based materials.
U.S. Pat. No. 4,147,640 to Jayne et al discloses improving lubricating oils by adding a reaction product obtained by reacting an olefinic hydrocarbon with sulfur and hydrogen sulfide. This produces an intermediate reaction product which is reacted with additional olefin hydrocarbons. The initial reaction is preferably carried out with a sulfurization catalyst. Those disclosed include quaternary ammonium salts, quanidines, thiuram sulfides and disulfides, alkyl and cycloalkyl amines, and still others. A catalyst is also used in the second stage such as a thiadiazole.
U.S. Pat. Nos. 4,119,549 and 4,191,659, both issued to Davis, disclose sulfurized compositions as lubricant additives in which the compositions are prepared by reacting under superatmospheric pressure an olefinic compound with a mixture of sulfur and hydrogen sulfide in the presence of an acidic, basic or neutral catalyst. A large number of materials is disclosed as useful catalysts. Neutral or acidic materials include acidified clays, p-toluene-sulfonic acid, and phosphorous sulfides such as phosphorous pentasulfide. Basic catalysts are preferred according to this patent and may include inorganic oxides and salts such as sodium hydroxide, calcium oxide and sodium sulfide. Nitrogen bases may also be used as catalysts such as ammonia and amines.